1. Field of Invention
This invention relates to a well completion process and more particularly to a well completion process in a wellbore which has an extended length exposed to a subterranean hydrocarbon bearing formation.
Historically, wellbores were drilled vertically, exposing the vertical cross-sectional height of the hydrocarbon bearing formation to the wellbore. Horizontal wells, which are currently being drilled, are drilled nearly perpendicular to the vertical axis of the formation to contact a greater amount of the formation. The horizontal portion of the wellbore is herein referred to as the lateral wellbore.
Horizontal and deviated wellbores are drilled laterally, penetrating thousands of feet of a hydrocarbon bearing formation. These bores intersect numerous porous and permeable hydrocarbon bearing zones. These intersected zones vary in permeability from secondary porosities such as open fractures and vugs which have darcies of permeability, to matrix porosities and closed fractures which have millidarcies of permeability. Hydrocarbon bearing zones which intersect the borehole vary in distribution and length within the wellbore. Some wells exhibit a number of small zones (less than 50 feet) randomly distributed in the wellbore, while other wells have hydrocarbon shows throughout the entire length of the lateral bore, which sometime exceed 5,000" in length.
The prior art indicates that the Oil and Gas Industry has attempted many forms of conventional vertical stimulation techniques in these extended horizontal wellbores. Ideally these hydrocarbon bearing zones are isolated and treated individually for the best result. A major obstacle and concern in the stimulation and treatment of horizontal bores has been the management, placement and distribution of treatment fluids into the numerous hydrocarbon bearing and non-hydrocarbon bearing zones exposed in the wellbore. Inability to isolate a segment of the exposed lateral renders many forms of conventional Oil and Gas stimulations ineffective because the necessary hydraulic horsepower cannot be delivered to the desired portion of the formation due to fluid losses in the remainder of the exposed wellbore. Other conventional stimulations which are not injection rate dependent are also rendered ineffective by the inability to create a path of least resistance into a desired interval or segment of the exposed lateral.
Mechanical isolation using casing, external casing packers, cement, and perforations have been mechanically difficult and cost prohibitive. Attempts to distribute treatment fluids into the numerous pay zones using fluid entrained diverting agents such as polymers, wax beads, rock salt, and the like have met with limited success. Dendritic or water fracs appear to be successful in some areas, but have also experienced failure in other areas.
The present invention provides a solution to the above problems by isolating and diverting treatment fluid in horizontal wellbores in a new and novel manner.